JP2630590B2 - Zero detector for magnetic encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a zero point detecting device for an incremental magnetic encoder using a magnetoresistive element.

(Prior Art) Conventionally, as an incremental magnetic encoder using a magnetoresistive element, a movable magnetic code recording member having a zero point detecting magnet and a plurality of incremental detecting magnets arranged at a predetermined magnetization pitch, A magnetoresistive element for zero point detection and a magnetoresistive element for incremental detection are disposed opposite to the two magnets at a predetermined distance, and a zero point signal obtained by a change in resistance of the magnetoresistive element for zero point detection is compared with, for example, a comparator. Is known to be converted into a zero-point pulse through.

The magnetizing width W of the zero point detecting magnet is 1/2 of the magnetizing pitch λ of the incremental detecting magnet, and a bias magnetic field is applied to the zero point detecting magnetic resistance element. FIG.
This shows a zero point signal.

(Problems to be Solved by the Invention) The above-described conventional magnetic encoder has a complicated structure, and the power supply voltage cannot be made too high in terms of allowable current.

That is, since the resistance cannot be increased so much with one magnetoresistive element, if the applied voltage is increased (for example, 12 V, 24 V, especially 24 V), the allowable current is exceeded and the magnetoresistive element is destroyed. Therefore, generally, the voltage applied to the magnetoresistive element is 5 V, and cannot be used with a power supply voltage of 24 V, for example.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a zero point detecting device for a magnetic encoder which can solve the conventional inconvenience and can reliably detect a zero point without being affected by disturbances such as fluctuations in power supply voltage. .

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a movable magnetic code having a zero point detecting magnet and a plurality of incremental detecting magnets arranged at a predetermined magnetization pitch. In a zero point detecting device for a magnetic encoder, wherein a recording member and a zero point detecting magnetoresistive element and an incremental detecting magnetoresistive element are disposed opposite to each other and at a predetermined distance from each other, the magnetizing of the zero point detecting magnet may be performed. The width W is set so that λ <W <3λ with respect to the magnetizing pitch λ of the incremental detection magnet, and the zero point detection magnetoresistive element is 0.5λ, 0.25λ along the moving direction of the magnetic code recording member. And 0.5λ
, A first magnetoresistive element, a second magnetoresistive element, a third magnetoresistive element, and a fourth magnetoresistive element, which are sequentially arranged at an interval of 1, and the first to fourth magnetoresistive elements are first, fourth, and fourth magnetoresistive elements. The third and second magneto-resistive elements are connected in series in this order, and the connection between the fourth and third magneto-resistive elements is used as an output terminal, and at both ends of the circuit of the series-connected magneto-resistive elements. A power supply voltage is applied.

(Operation) The resistance of a circuit in which four magnetoresistive elements are connected in series becomes large, and the current flowing through the circuit is increased even if the power supply voltage applied to both ends of the circuit is high, for example, 24V. The current is less than the allowable current of the element. In addition, as a result of repeated experiments, the inventor has found that due to the above-described configuration, resetting for zero point detection cannot be performed due to disturbance such as power supply voltage fluctuation,
Alternatively, it has been found that a zero-point pulse in which an error does not occur due to a change in the zero-point detection point is obtained from the comparator connected to the output terminal.

(Example) An example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 designates a magnet for detecting a zero point.
Together with this, a magnetic code recording member 3 movable in the direction of the arrow is formed. The magnetization width W of the zero point detecting magnet 1 is, for example, 0.25.
In mm, it is set so that λ <W <3λ with respect to the magnetization pitch λ of the incremental detection magnet 2. 4 ₁ , 4
_2, 4 _3, 4 ₄ 0.5 [lambda along the moving direction of the magnet 2 within the track 5 zeros detecting magnets 1, magnetoresistive elements which are sequentially arranged at intervals of 0.25λ and 0.5 [lambda, magnetic Resistance elements 4 ₁ , 4 ₂ ,
4 ₃ and 4 ₄ are disposed together with an incremental detection magnetoresistive element (not shown) on the lower surface of, for example, a glass substrate 6 provided at a predetermined distance from the magnetic code recording member 3, for example, at the aforementioned magnetic pitch λ. , Magnetoresistive elements 4 ₁ , 4 ₄ , 4 ₃ , 4
Is connected in series with a _second order, the first magneto resistive element 4 ₁ is for example 12V DC second magnetoresistance element 4 ₂ ,, is connected to the terminal 7 of the current is grounded, the third and fourth magnetoresistance elements 4 ₃ and 4 ₄ connecting terminals 8, as shown in FIG. 2, is connected to the comparator 9.

Here, the magnetoresistive elements 4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ are, for example, twelfth.
As shown in the figure, the resistance value R changes according to the strength of the magnetic field H in a direction orthogonal to the direction of the current. When no magnetic field is applied, the resistance value is maximum, and when the strength of the magnetic field increases, the resistance value decreases. It has the characteristics to go.

The reference level of the comparator 9 connected to the connection terminal 8 is the pulse of the zero-point pulse Zp output from the comparator 9 even if the power supply voltage fluctuates and the level rises and falls (up and down width p) as shown in FIG. width hardly changes significantly, and noise n is zero signal Z ₅ to zero pulse Z incorrect be mixed
p 'is set to a level L ₁ remembering a margin y is not output. (Level L pulse width of ₂ in the zero point pulse Zp greatly changes, and outputs the erroneous Level L ₃ zeros pulse Zp '.) Note that Figure 3 - Figure 8 and Figure 10, the vertical Figure 11 On the axis,
The midpoint potential of the connection terminal 8 shown in FIG.
Is shown as the zero point potential.

Now, when the magnetization width W of the zero point detection magnet 1 is set to W = 1.5λ with respect to the magnetization pitch λ of the incremental detection magnet 2, the zero point signal obtained from the connection terminal 8 is as shown in FIG. , 0.66Ramuda the reference level L ₁ remembering the margin y of 6mV
A zero-point pulse having a pulse width of

When W = 2λ and W = 2.5λ, the zero point signals as shown in FIGS. 5 and 6 and 0.85λ and 1.
A zero pulse with a pulse width of 1λ was obtained.

The above-mentioned zero-point pulses having pulse widths of 0.66λ, 0.85λ, and 1.1λ are zero-point pulses that can reliably detect a zero point without being affected by disturbance such as a fluctuation in power supply voltage.

Comparative Example The magnetization width W of the zero point detection magnet 1 is set to be W = 0.8λ and W = λ with respect to the magnetization pitch λ of the incremental detection magnet 2.
Then, a zero point signal as shown in FIGS. 7 and 8, and a zero point pulse Zp having a pulse width PW of 0.2λ and 0.46λ were obtained.

PW <When the 0.5 [lambda, as shown in FIG. 9, the rising portion B ₁ is a pulse width of zero pulse Zp incremental signal Is
When set to the PW, will position the rising portion of the B ₂ incremental signal Is by the disturbance, the rising portion of the zero point pulse Zp becomes the position of C ₂ from C _1, the rising portion of the incremental signal Is pulse width PW of B ₂ is zero pulse Zp
And resetting for zero detection may not be possible.

Further, the magnetization width W is defined as W = W
When 3λ is set, the zero point signal and PW as shown in FIG.
A zero point pulse Zp with a pulse width of = 1.1λ was obtained.

Reference pulse L ₁ of the comparator 9 in this case zero point signal
Located closer to the maximum amplitude of zs, hence the reference level greatly varies the pulse width PW of the zero point pulse when varied up and down by variation of the power supply voltage, the rising portion of the incremental signal Is (9 see FIG numeral B ₁ ) May be out of the pulse width PW of the zero point pulse and reset may not be possible.

(Effect of the Invention) As described above, according to the present invention, the power supply voltage can be increased to, for example, 24 V, and the power supply voltage can be affected by disturbances such as fluctuations of the power supply voltage without complicating the structure. Therefore, there is an effect that the zero point can be detected without fail.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of one embodiment of the present invention, FIG. 2 is a circuit diagram thereof, FIGS.
(A) and (B) of FIG. 5, FIG. 5 and FIG. 6 are waveform diagrams of the zero point signal and the zero point pulse of the embodiment of the present invention, respectively.
FIGS. 8A and 8B are waveform diagrams of a zero-point signal and a zero-point pulse of a comparative example, respectively, and FIGS. 9A and 9B are operation explanatory diagrams of one comparative example, and FIGS. 11A and 11B are waveform diagrams of a zero-point signal and a zero-point pulse of another comparative example, FIG. 11 is a waveform diagram of a zero-point signal of a conventional example, and FIG. FIG. 1 ...... zero detecting magnet 2 ...... incremental detecting magnet 4 _1, 4 _2, 4 _3, 4 ₄ ...... magnetoresistive element 9 ...... comparator

Claims (1)

(57) [Claims] 1. A movable magnetic code recording member having a plurality of incremental detection magnets arranged at a predetermined magnetization pitch with a zero detection magnet, and a zero point which is respectively opposed to the two magnets and is separated by a predetermined distance. In the zero point detecting device of the magnetic encoder provided with the detecting magnetic resistance element and the incremental detecting magnetic resistance element, the magnetization width W of the zero detection magnet is λ <W with respect to the magnetization pitch λ of the incremental detection magnet. <3λ, and the zero point detecting magnetoresistive element is moved along the moving direction of the magnetic code recording member.
A first magnetoresistive element, a second magnetoresistive element, a third magnetoresistive element and a fourth magnetoresistive element which are sequentially arranged at intervals of 0.5λ, 0.25λ and 0.5λ; Are connected in series in the order of the first, fourth, third and second magnetoresistive elements, and the connection between the fourth and third magnetoresistive elements is used as an output terminal and connected in series. A zero point detecting device for a magnetic encoder, wherein a power supply voltage is applied to both ends of a circuit of a magnetoresistive element.